Show the formula and working
This cm to inches converter changes centimetres into inches, and inches back into centimetres, for shoppers, DIYers and crafters in the UK, Ireland and the rest of Europe who meet American or older British sizes. Enter a length and you get decimal inches, the nearest sixteenth of an inch as on a tape measure, and feet and inches.
Quick answer: To convert cm to inches, divide the centimetres by 2.54, because one inch is exactly 2.54 cm. So 30 cm is 11.81 inches, about 11 13/16 in on a tape measure, and 100 cm is 39.37 inches. To go back, multiply inches by 2.54: 12 inches is 30.48 cm.
What Is a Cm to Inches Converter?
A cm to inches converter is a tool that turns a length in centimetres into the same length in inches. The formula is inches equal centimetres divided by 2.54. For the reverse, centimetres equal inches multiplied by 2.54.
The factor is exact, not rounded. Since 1959 the international inch has been defined as exactly 25.4 mm, as NIST sets out, and UK law in the Weights and Measures Act 1985 defines the inch as one thirty sixth of a yard of 0.9144 m, which gives the same 2.54 cm.
How Do You Use the Cm to Inches Converter?
- Choose the Direction: “Cm to inches” or “Inches to cm”.
- Type the Amount: centimetres for Cm to inches, or inches for Inches to cm. Write fractions of an inch as decimals, so 5 1/4 in is 5.25.
- For cm to inches, read decimal inches plus the nearest sixteenth of an inch, which matches the marks on an imperial tape measure, and the length in feet and inches.
- Read the result, then open “Show the formula and working” to see the division and the rounding to sixteenths.
How Many Inches Is 1 Cm?
One centimetre is 0.3937 inches, a little under four tenths of an inch. So 2.5 cm is very nearly 1 inch, which is a useful rule of thumb when you have no calculator: count roughly 2.5 cm per inch, or 10 cm for every 4 inches. For anything you need to fit, such as a shelf or a curtain pole, use the exact 2.54 instead, because the rule of thumb loses about 1.6% over the length.
How Do You Convert Cm to Inches in Your Head?
Multiply the centimetres by 4 and divide by 10 for a close estimate. For 30 cm, 30 x 4 is 120 and divided by 10 is 12 inches, against the exact 11.81 inches. The shortcut slightly overstates inches because it treats an inch as 2.5 cm. It is fine for clothes and rough checks, but not for kitchen worktops or flat pack furniture, where a few millimetres matter.
How Do You Read Cm as Inches on a Tape Measure?
Imperial tape measures split each inch into 16 parts, so round the decimal inches to the nearest sixteenth. Multiply the decimal part by 16 and round: 11.81 inches is 11 plus 0.81 x 16 = 12.98 sixteenths, so 11 13/16 in. The converter does this for you and reduces the fraction, so 8 sixteenths shows as 1/2 and 12 sixteenths as 3/4.
Cm to Inches Conversion Table
| Centimetres | Inches (decimal) | Nearest 1/16 inch |
|---|---|---|
| 1 cm | 0.39 in | 3/8 in |
| 2 cm | 0.79 in | 13/16 in |
| 2.5 cm | 0.98 in | 1 in |
| 5 cm | 1.97 in | 1 15/16 in |
| 10 cm | 3.94 in | 3 15/16 in |
| 15 cm | 5.91 in | 5 7/8 in |
| 20 cm | 7.87 in | 7 7/8 in |
| 25 cm | 9.84 in | 9 13/16 in |
| 30 cm | 11.81 in | 11 13/16 in |
| 40 cm | 15.75 in | 15 3/4 in |
| 50 cm | 19.69 in | 19 11/16 in |
| 100 cm | 39.37 in | 39 3/8 in |
Worked Example: Will the Bookcase Fit?
Example: an alcove beside a chimney breast measures 76 cm wide, and the bookcase you like is listed by an American seller as 30 inches wide. Leave the Direction on “Cm to inches” and enter 76 as the Amount. The converter divides 76 by 2.54 and shows 29.92 inches, or 29 15/16 in to the nearest sixteenth. The bookcase is 0.08 inches, about 2 mm, wider than the alcove, so it will not fit.
Tile and trim sizes are often quoted in both systems. Once you have converted, the tile calculator works out how many tiles a wall or floor needs, and the skirting board calculator works out lengths to buy. You will find more in our home calculators.
Cm to Inches Converter FAQs
How many cm is 1 inch?
One inch is exactly 2.54 centimetres, or 25.4 millimetres. This has been the international definition since 1959 and is the same in the UK, the US and every other country. Multiply inches by 2.54 to get centimetres.
How many inches is 30 cm?
Thirty centimetres is 11.81 inches, or 11 13/16 in to the nearest sixteenth. That is why a 30 cm school ruler is a little shorter than a 12 inch ruler, which measures 30.48 cm. The difference is just under 5 mm.
What is 32 inches in cm?
Thirty two inches is 81.28 cm. Multiply 32 by 2.54 to get it. This is a common waist and inside leg size on jeans, and in the converter you set Direction to “Inches to cm” and enter 32 as the Amount.
How many inches is 100 cm?
One hundred centimetres, which is one metre, equals 39.37 inches, or 3 ft 3.4 in. A metre is therefore about 3.4 inches longer than a yard of 36 inches, which is a handy comparison when buying fabric sold by the metre.
Is 2.5 cm an inch?
Nearly, but not exactly. 2.5 cm is 0.984 inches, while one inch is exactly 2.54 cm. The 0.4 mm gap is tiny for a single inch, but over 10 inches it grows to 4 mm, enough to matter for furniture and fittings.
How do you convert cm to feet and inches?
Divide the centimetres by 2.54 to get inches, then divide by 12: the whole number is feet and the remainder is inches. For 170 cm, that is 66.93 inches, or 5 ft 6.9 in. The converter shows this under Feet and inches.
Checked October 2026. Sources: NIST: SI units, length, Weights and Measures Act 1985, Schedule 1 (legislation.gov.uk), Inch (Wikipedia).